Dec. 13 (UPI) -- The benefit from using a premium blend of gasoline in a vehicle that doesn't require it may not be worth the extra cost for some U.S. drivers, motor club AAA said.
AAA reported a national average retail price for regular unleaded gasoline at $2.46 for Wednesday, more or less stable for the week. The average price for premium gasoline was $3 per gallon.
The motor club said its research showed that the difference between regular- and premium-grade gasoline has increased from a historic norm of 10 percent to now at least 25 percent. For some vehicles, the higher octane premium blend means an improved fuel economy and better vehicle performance overall.
"AAA's testing reveals that drivers could see modest gains in fuel economy and performance when opting for premium gasoline in vehicles that recommend, but do not require, the higher-octane fuel," Megan McKernan, manager of the Automobile Club of Southern California's Automotive Research Center, said in a statement.
Results were mixed, according to on-road and laboratory tests. The 2016 Cadillac Escalade showed a fuel economy improvement of more than 7 percent, while the 2016 Audi A3 actually saw fuel economy drop by 1 percent. For horsepower, the 2016 Jeep Renegade bogged by 0.3 percent with premium fuel, while the 2017 Ford Mustang showed a 3.2 percent improvement.
McKernan said that drivers looking for a boost might see some gains with a higher-octane fuel, especially long term. Nevertheless, the motor club said in study coordinated with McKernan's group that the benefits might not offset the cost, especially for a vehicle that doesn't require the premium blend.
"Based on AAA's testing, vehicles that only recommend premium gasoline can't take full advantage of higher octane fuel and, as a result, the benefit that comes from upgrading to premium gasoline may not offset its high cost," John Nielsen, AAA's managing director of engineering and repair, said.
The motor club estimated that 1.5 million new vehicles were sold last year that had manufacturer recommendations for a higher-octane fuel, but don't actually require it.
U.S. refineries switch late in the year to a winter-blend of gasoline, which is less expensive to make because more steps are needed with the summer-blend to prevent excessive evaporation. As a result, summer blends improve gas mileage.